The Multiplexed Design of Neurons

In 1910, Major General George Owen Squier developed a technique to increase the efficiency of data transmission along telephone lines that is still used today in telecommunications and computer networks. This technique, called multiplexing, allows multiple signals to be combined and transmitted along a single cable, making it possible to share a scarce resource (available phone lines, in Squier’s day).

Today, there are a number of ways to carry out multiplexing. One of them is called time-division multiplexing. While other forms of multiplexing can be used for analog data, this technique can only be applied to digital data. Data is transmitted as a collection of bits along a single channel separated by a time interval that allows the data groups to be directed to the appropriate receiver.

Researchers from Duke University have discovered that neurons employ time-division multiplexing to transmit multiple electrical signals along a single axon.1 The remarkable similarity between data transmission techniques used by neurons and telecommunication systems and computer networks is provocative. It can also be marshaled to add support to the revitalized Watchmaker argument for God’s existence and role in the origin and design of life.

A brief primer on neurons will help us better appreciate the work of the Duke research team.

Neurons

The primary component of the nervous system (the brain, spinal cord, and the peripheral system of nerves), neurons are electrically excitable cells that rely on electrochemical processes to receive and send electrical signals. By connecting to each other through specialized structures called synapses, neurons form pathways that transmit information throughout the nervous system.

Neurons consist of the soma or cell body, along with several outward extending projections called dendrites and axons.

Image credit: Wikipedia

Dendrites are “tree-like” projections that extend from the soma into the synaptic space. Receptors on the surface of dendrites bind neurotransmitters deposited by adjacent neurons in the synapse. These binding events trigger an electrical signal that travels along the length of the dendrites to the soma. However, axons conduct electrical impulses away from the soma toward the synapse, where this signal triggers the release of neurotransmitters into the extracellular medium, initiating electrical activity in the dendrites of adjacent neurons.

Sensory Neurons

In the world around us, many things happen at the same time. And we need to be aware of all of these events. Sensory neurons react to stimuli, communicating information about the environment to our brains. Many different types of sensory neurons exist, making possible our sense of sight, smell, taste, hearing, touch, and temperature. These sensory neurons have to be broadly tuned and may have to respond to more than one environmental stimulus at the same time. An example of this scenario would be carrying on a conversation with a friend at an outdoor café while the sounds of the city surround us.

The Duke University researchers wanted to understand the mechanism neurons employ when they transmit information about two or more environmental stimuli at the same time. To accomplish this, the scientists trained two macaques (monkeys) to look in the direction of two distinct sounds produced at two different locations in the room. After achieving this step, the researchers planted electrodes into the inferior colliculus of the monkeys’ brains and used these electrodes to record the activity of single neurons as the monkeys responded to auditory stimuli. The researchers discovered that each sound produced a unique firing rate along single neurons and that when the two sounds were presented at the same time, the neuron transmitting the electrical signals alternated back and forth between the two firing rates. In other words, the neurons employed time-division multiplexing to transmit the two signals.

Neuron Multiplexing and the Case for Creation

The capacity of neurons to multiplex signals generated by environmental stimuli exemplifies the elegance and sophistication of biological designs. And it is discoveries such as these that compel me to believe that life must stem from the work of a Creator.

But the case for a Creator extends beyond the intuition of design. Discoveries like this one breathe new life into the Watchmaker argument.

British natural theologian William Paley(1743–1805) advanced this argument by pointing out that the characteristics of a watch—with the complex interaction of its precision parts for the purpose of telling time—implied the work of an intelligent designer. Paley asserted by analogy that just as a watch requires a watchmaker, so too, does life require a Creator, since organisms display a wide range of features characterized by the precise interplay of complex parts for specific purposes.

Over the centuries, skeptics have maligned this argument by claiming that biological systems only bear a superficial similarity to human designs. That is, the analogy between human designs and biological systems is weak and, therefore, undermines the conclusion that a Divine Watchmaker exits. But, as I discuss in The Cell’s Design, the discovery of molecular motors, biochemical watches, and DNA computers—biochemical complexes with machine-like characteristics—energizes the argument. These systems are identical to the highly sophisticated machines and devices we build as human designers. In fact, these biochemical systems have been directly incorporated into nanotechnologies. And, we recognize that motors and computers, not to mention watches, come from minds. So, why wouldn’t we conclude that these biochemical systems come from a mind, as well?

Analogies between human machines and biological systems are not confined to biochemical systems. We see them at the biological level as well, as the latest work by the research team from Duke University illustrates.

It is fascinating to me that as we learn more about living systems, whether at the molecular scale, the cellular level, or the systems stage, we discover more and more instances in which biological systems bear eerie similarities to human designs. This learning strengthens the Watchmaker argument and the case for a Creator.

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